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问题 选择题

汽车安全气囊内的物质在汽车受到碰撞时会迅速生成一种空气里含量最多的气体，从而保护驾乘人员减少损伤，该种气体是（　　）

A．氧气

B．水蒸气

C．二氧化碳

D．氮气

答案

空气的组成按体积计算，大约是氮气78%，氧气21%，稀有气体0.94%，二氧化碳0.03%，其它气体和杂质0.03%，空气里含量最多的气体是氮气．故D正确．

故选D．

单项选择题

It is clear that some chemicals can damage the health of animals and humans. (1) , this is not the only problem that (2) be caused by the careless use of chemicals. Chemicals can also (3) the ecological balance of the environment. If the ecological balance is disturbed, the results can be (4) serious.The (5) of DDT illustrates the problem. DDT, a chemical which kills insects, at first seemed to be a perfect answer (6) many problems. It would control insects that caused dangerous diseases, (7) insects that caused billions of dollars of damage to crops every year. Governments permitted and even (8) the use of DDT. Farmers in many countries (9) to spray it on their crops. The (10) results were good. Damage to crops (11) down, and profits went up. However, the chemical had effects which the scientists didn’t see in (12) . First, it also killed insects which were the (13) enemies of the harmful insects and which were therefore beneficial to farmers. Second, and perhaps worse, DDT did not kill (14) harmful insect. A few insects had natural resistance to the chemical. They (15) and reproduced in large numbers. In a few years there were large numbers of insects which were not (16) by DDT, and there were (17) insects which Could act as natural (18) on these new "super-insects". Finally, it became clear that DDT was not solving the insect problem. In fact, it was making the problem worse. It (19) became necessary to find a second (20) for the effects of the first.

 

第（9）空应选择（）

A．wanted

B．began

C．decided

D．arranged
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单项选择题

恶性淋巴瘤以下列哪一部位淋巴结肿大最为常见（）

A.颌下

B.腹股沟

C.腋下

D.颈部

E.耳后
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